Before: Save g:ale_c_clangformat_executable " Use an invalid global executable, so we don't match it. let g:ale_c_clangformat_executable = 'xxxinvalid' call ale#test#SetDirectory('/testplugin/test/fixers') silent cd .. silent cd command_callback let g:dir = getcwd() After: Restore call ale#test#RestoreDirectory() Execute(The clang-format callback should return the correct default values): call ale#test#SetFilename('c_paths/dummy.c') AssertEqual \ { \ 'command': ale#Escape(g:ale_c_clangformat_executable) \ . ' ' \ }, \ ale#fixers#clangformat#Fix(bufnr('')) Execute(The clangformat callback should include any additional options): call ale#test#SetFilename('c_paths/dummy.c') let g:ale_c_clangformat_options = '--some-option' AssertEqual \ { \ 'command': ale#Escape(g:ale_c_clangformat_executable) \ . ' --some-option', \ }, \ ale#fixers#clangformat#Fix(bufnr(''))